Clutch Wear Percentage???

Wait until it starts to slip, but at that point don't delay. I have seen them work well at # over 100 and go bad below 100. The machine generated # is only an estimation and it can be manipulated somewhat.

 

the SD-2 unit uses a mathematical algorithm to estimate clutch wear. There is no actual sensor looking at the clutch. In addition, the machines vary from machine to machine, and day to day. I had clutch wear on my 360 CH diagnosed one morning at Pocono at 2%, the next day with a different unit at 56%. A year later no problems, same clutch. Just wait until it dies a natural death.

 

Now I don’t know the exact 355 mechanism, however with the 360 F1 is a closed loop system, i.e. it has a sensor for clutch travel. Clutch wear is calculated from the position the clutch is closed when new and the position when the clutch is closed at the last time the car has been started, i.e. the delta

distances are all in millimeters and change significantly when the clutch is stone cold or when it is hot – so it is important to do this with a stone cold engine as reference point - as far as I remember F suggests to replace the clutch at 80% wear rate

however the only sure way is to remove the underbody and open the inspection hole and physically measure - again not sure if the 355 has this too

 

You are correct as to the method of the SD2 determining clutch wear and the fact that it is temperature sensitive. I said earlier that it was an estimation. That was a misstatement, it is measured but not very acurately or consistantly.

However it has never been Ferrari's position to replace it at 80%. They have never offered an official position on that. An individual or a dealer might have. I have seen many showing over 100% and still working good and there is no down side to waiting until it is all gone. The pressure plate will lose clamping force and the clutch will slip long before any metal to metal damage can take place. You can sense the clutch being worn out or slipping just as you can any clutch equipped car so there is no need to rely on the machine telling you when to do it.

 

There is indeed an actual sensor, I have changed many. You can even see it through a hole in the bell housing under the car.

 

Does this only apply to cars with the F1 transmission?

 

Yes.

 

Thanks Brian. Your help on this list is greatly appreciated!

 

Personally I would not like to wear down the clutch until it slips especially with the F1

Clutch wear in my case is around 15% per 10K miles (don’t do a lot of city driving but track the car)

Taking the service interval of 15K miles we are looking at 20% clutch wear – this all makes sense to me considering the 360 clutch design (small)

So I figured a 20% safety margin is actually a sensible thing; i.e. dealers replacing the clutch at 80% sound ok to me - I would hate to actually have the clutch start slipping on one of my trips not to think about what the stupid transmission TCU will do to me if it gets confused

Can you max the clutch life by going to 99% (assuming that the clutch wear parameter is a well defined parameter) – sure – however the car is my hobby and all I want is to have fun driving it

 

No two people are going to wear out a clutch, even a computer controlled one at the same rate. Also even though it is computer controlled you will (or you do) get a feel when driving how worn the clutch is, in much the same way you would if you were operating it with a pedal. The point here is that you will not just wake up one morning with a worn out clutch. It will give you all the signs any other clutch you have worn out did and when that happens just replace it.

 

I have seen a few cases on 355's when they did not register any. But that is rare. 355's record overheat in seconds, 360's record in minutes. Due to that 360's often have none in record but as I said that is pretty rare in a 355. If you keep it under 2-3 minutes total you are doing pretty good, if you get into double digits I will probably know it by looking at the heat damage when I replace the clutch.

 

If you are referring to the SDII reader being different from unit to unit is a scary thought. If I understand it correctly it is the ECU/TCU which makes the measurement and SDII just reports it. Plus there must be calibration routines to make sure from unit to unit variability is within a certain range otherwise why devise a test that would provide grossly wrong numbers.

 

Matt you are correct it is just reading info that is in the cars memory. The reading will vary a little from reading to reading on the same car as we spoke of before in this thread. A difference of the magnitude he reported suggests either a problem with the car or the equipment. The problem that comes to my mind is a sticking TO brng which you experienced in your car.